Development Flashcards
What’s the difference between pluripotent, totipotent, and multipotent? How can you relate a spermatogonium, a primary spermatocyte, and a spermatid? Use these cards to see how all of these topics connect, and you can master reproduction and development as tested on the MCAT.
What is the function of the reproductive system?
The reproductive system generates new offspring from parent organisms, facilitating the survival of the species.
Some reproductive methods also increase genetic variation. This allows a species to adapt to changes in its environment.
What is the difference between sexual and asexual reproduction?
Sexual reproduction involves two organisms and results in offspring that genetically differs from both of them. Asexual reproduction is carried out by a single organism and produces genetically identical offspring.
All prokaryotes use asexual reproduction, though they have alternative methods of gene transfer. Eukaryotic species can reproduce sexually, asexually, or through both mechanisms.
Define:
gamete
A gamete is a haploid cell that combines with another gamete during sexual reproduction. Together, the fused cells form a zygote that develops into a new organism.
In humans, the male gamete is the sperm while the female gamete is the egg or ovum.
Label the parts of the sperm cell below.
What is spermatogenesis, and when and where does it begin?
Spermatogenesis is the production of the male gametes, sperm, in the seminiferous tubules of the testes.
Spermatogenesis begins at puberty.
Order the following terms from least to most mature: spermatid, spermatogonium, spermatozoon, secondary spermatocyte, primary spermatocyte.
The least mature (most undifferentiated) cell is the spermatogonium, followed by the primary spermatocyte, secondary spermatocyte, and spermatid. A fully mature sperm cell is known as a spermatozoon.
Both meiosis and mitosis are involved in this differentiation process.
During which step of spermatogenesis do cells become haploid?
Developing cells become haploid during meiosis I, which is the division from primary to secondary spermatocyte. After this transition, the gamete will be haploid but with replicated chromosomes.
Meiosis II, on the other hand, refers to the division from secondary spermatocyte to spermatid. After this step, the gamete will be haploid with only one copy of each chromosome, as in its final state.
Around what age in men does sperm production cease?
Spermatogenesis never ceases; it continues throughout a man’s adult life.
In contrast, oogenesis does not occur as a steady process. Virtually all of a woman’s eggs are partially differentiated by birth, and all differentiation ceases completely at menopause.
What is oogenesis, and where and when does it begin?
Oogenesis is the production of the female gametes, ova, in the ovaries.
Oogenesis begins before birth. Specifically, all of a female’s oocytes are produced and arrested at prophase I by the time she is born.
Order the following terms from least to most mature: primary oocyte, ovum, oogonium, secondary oocyte.
The least mature (most undifferentiated) cell is the oogonium, followed by the primary oocyte, secondary oocyte, and ovum.
Both meiosis and mitosis are involved in this diffferentiation process.
Define:
polar body
A polar body is a haploid cell produced by meiosis I or meiosis II of oogenesis. Though they possess normal amounts of genetic material, polar bodies contain little cytosol and few organelles.
Oogenesis is thus characterized by uneven division of cytoplasm. Most of the cytoplasm is allocated to the functioning oocyte, while little is given to the polar body.
How many cells are produced in the differentiation of one primary oocyte into one mature ovum?
Oogenesis produces three cells per primary oocyte: one ovum and two polar bodies.
In meiosis I, the primary oocyte divides into one secondary oocyte and one polar body. This first polar body generally does not divide further. If fertilized, the secondary oocyte undergoes meiosis II, where it divides into one ovum and a second polar body.
From birth until puberty, all of a female’s oocytes are arrested at which stage of oogenesis?
All of a female’s oocytes are primary and are arrested in prophase I of meiosis.
Meiosis I corresponds to which step of oogenesis?
In oogenesis, meiosis I involves the division of a primary into a secondary oocyte.
Meiosis II, which is only completed if the egg is fertilized, involves the division of this secondary oocyte into a mature ovum.
Name two differences between spermatogenesis and oogenesis.
- Spermatogenesis produces four equally functional gametes, while oogenesis produces one mature ovum and two nonfunctional polar bodies.
- Spermatogenesis takes place continuously from puberty to death, while oogenesis begins before birth and ends at menopause.
Which gamete contributes mitochondria to the developing zygote?
A zygote’s mitochondria are contributed by the ovum.
While sperm contain mitochondria, they are destroyed by the ovum shortly after fertilization. As a result, mitochondrial diseases are inherited maternally.
Define:
gonads
The gonads are endocrine organs that produce gametes.
The female gonads are the ovaries while the male gonads are the testes.
What is an androgen?
An androgen is a general term for a hormone that influences male development.
The most important androgen to know is testosterone, a steroid hormone.
Name the major male and female sex hormones.
The most important sex hormones are testosterone in males and estrogen and progesterone in females.
While these hormones are steroids, their production is closely related to that of the peptides FSH and LH.
Give two structural differences between the male and female reproductive systems.
- Male reproductive organs are mainly found outside of the body, while female organs are located internally.
- In males, the urethra serves both reproductive and urinary purposes, while in females, it is only involved in urination.
Define:
puberty
Puberty is the period of the human lifespan during which the reproductive system becomes mature.
In females, this process is marked by menarche, or the first menstrual period. In males, spermatogenesis begins at puberty.
In females, which process involves a decrease in sex hormones and the halting of ovulation?
Menopause
Specifically, menopause is the period when menstrual cycles stop occurring and a female can no longer become pregnant.
On the diagram below, label the ovaries, Fallopian tubes, uterus, and vagina.
What is another term used for the Fallopian tubes?
The oviducts
Each Fallopian tube connects a single ovary to the uterus.
What are follicles, and in which female reproductive structure are they located?
Follicles are multicellular structures located within the ovaries. Each follicle surrounds and nourishes a single oocyte.
During ovulation, the follicle bursts and develops into the corpus luteum.
Once every 28 days, one follicle ruptures inside the ovary, releasing an oocyte into the Fallopian tube. What term is used to refer to this process?
The release of an oocyte from the ovary is called ovulation.